Can't say that I've seen this before, nor can I seem to reproduce it with any kind of consistency. But it is something 'new', no? Friend of the Dojo, Mike Wilton, shared the discovery today after noticing it while searching for the term [tarantula]. Here's a screen to explain..

The two listings there in the Google suggest drop down seem to be entity expansions based on the knowledge graph updates and leads to query refinements like so;